.\"	$OpenBSD: getpgrp.2,v 1.17 2013/03/31 19:23:08 guenther Exp $
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.\"     @(#)getpgrp.2	8.1 (Berkeley) 6/4/93
.\"
.Dd $Mdocdate: March 31 2013 $
.Dt GETPGRP 2
.Os
.Sh NAME
.Nm getpgrp ,
.Nm getpgid
.Nd get process group
.Sh SYNOPSIS
.Fd #include <unistd.h>
.Ft pid_t
.Fn getpgrp "void"
.Ft pid_t
.Fn getpgid "pid_t pid"
.Sh DESCRIPTION
The process group of the current process is returned by
.Fn getpgrp .
The process group of the
.Fa pid
process is returned by
.Fn getpgid .
If
.Fa pid
is zero,
.Fn getpgid
returns the process group of the current process.
.Pp
Process groups are used for distribution of signals, and
by terminals to arbitrate requests for their input: processes
that have the same process group as the terminal are foreground
and may read, while others will block with a signal if they attempt
to read.
.Pp
These calls are thus used by programs such as
.Xr csh 1
to create
process groups
in implementing job control.
The
.Fn tcgetpgrp
and
.Fn tcsetpgrp
calls
are used to get/set the process group of the control terminal.
.Sh ERRORS
.Fn getpgrp
always succeeds, however
.Fn getpgid
will succeed unless:
.Bl -tag -width Er
.It Bq Er EPERM
The current process and the process
.Fa pid
are not in the same session.
.It Bq Er ESRCH
There is no process with a process ID equal to
.Fa pid .
.El
.Sh SEE ALSO
.Xr setpgid 2 ,
.Xr termios 4
.Sh STANDARDS
The
.Fn getpgrp
and
.Fn getpgid
functions conform to
.St -p1003.1-2008 .
.Sh HISTORY
A
.Fn getpgrp
function call that took a
.Fa "pid_t pid"
argument appeared in
.Bx 4.0 .
This version, without an argument, is derived from its usage in
System V Release 4, and first appeared in
.Nx 0.9 .
.Pp
The
.Fn getpgid
function call is derived from its usage in System V Release 4, and
first appeared in
.Nx 1.2a .
